Brake



March 23, 1937. E. G CAROLPL 2,074,719 BRAKE Original Filed April 13, 1932 s SheetsSheet 1 7 Z 9 Z INVENTOR.

' EUGENE G, CQEEOLL BY m A):

- MTTORNEY,

Mara] 23, 1937. E G, cAR bLL 2,074,719

- BRAKE Original Filed April 15, 1932 5 Sheets-Sheet 2 INVEN TOR. EUGENE G. CQBB LL ATTORNEY.

Patented Mar. 23, 1937 i BRAKE Eugene G. Carroll, Los Angeles, Calif., asslgnor to Bendix Aviation Gorporation, Ind, a corporation of Delaware South Bend,

Application April 13, 1932, Serial No; 665,083

Renewed September 3, 1935 This invention relates to brakes and more especially to hydraulic operating systems therefor.

One of the objects of myinvention is to provide improved means for developing and maintaining a superatmosphericpressure acting upon the liquid in a hydraulic. brake system so as to keepthe'operating part of the system full of liquid at all times and to eliminate the springy pedal accompanying the presence of air mixed.

with the liquid in said operating partof the sysi tem. i T

A further object-of the invention is to provide improved ,means vfor preventing the ingress of air into the operating parts of the system and especially into the wheel cylinders thereof.

Further-objects. of the invention will be apparentafter'a readingof the subjoined specificatlon and claims and after a consideration of the attached drawings in which: a

I 0 Figure 1 is a view'showing, more orless diagrammatically, parts of a hydraulic braking system including a-mastercylinder, a wheelcylinder, and connections between the master cylinder and the-wheel cylinder; r

0 1 Figure 2 is a view showing a modified system of hydraulic brakes;

v Figure 3 is a view showing a modified form of master cylinder adapted to be substituted for the master cylinder shown in Figure 1; and

Figure .4 is a; view showing "another modified form ofmaster cylinder also adapted to be substituted for the master cylinder shown, in Fig-- urel. 7

Referring in particular-to the drawings, there is shown in Figure l, a master cylinder generally a designated II, a wheel cylinder generally designated l2 and fluid connections indicated by the linel3. The'cylinder [I is formed of a casting having a forwardly extending cylindrical portion I51 and a rearwardly extending "cylindrical portion l6 having a larger diameter; On the underside of the casting l4 there is formed a downwardly extending'bracket .IT by whichthe cylinder ll maybe secured to an automotive vehicle. The upper sideof the castihg'is formed with an annular. flange l8 forming a well and is exteriorly threadedas'at 19 for the receptionof a cover which is designedrto coactwith the frame to serve as a fluid reservoir. 1

with threads 2| for thereception of an outlet cap 22; It has a restricted inlet port 23 formed 1 through thecylindrical portion 15 andppening into the well formed bythe annular flange l8 and has a relatively large port 24: extending diagonally an annular sealingcup 42.

The casting II (is formed atits forward end through the junction between the concentric cylindrical portions i5 and IS. The rear end of the casting is providedwith an annular flange 25 by means of which a boot may be secured to the casting. l

Secured on the threads I9 is a cylindrical cover 26 which serves together with the well formed by the flange l8.to provide a container or reservoir for a reserve supply of liquid for the hydraulic braking system. The upper end of the cap 26 isformed with a cylmdrical depression 21 having anopening 28 in the center thereof. A plug 29 having a vent opening 3| is screwed into the depression 21 and serves'as an abutment for a compression spring 32 which'bears at its lower end upon a cup, valve 33. The spring 32 is of such a weight that pressure within thereservoir' may be increased toa certain pre-determined amount before anyfluid can escape past the valvewhich thus constitutes'a spring loaded valve.

The cap 22 is provided with a tapped opening 20 into which thereis threaded a pipe forming a portion of the connection l3. Secured to the rear end of the casing l4 by means of, the'flange 25 is a rubber boot 34 which serves to exclude (lust and dirt but allows the ingress of air through: an opening 35. -Passing' through theboot 34 and secured thereto by a spring clip 36 is a piston rod 31 which is connected in any convenient manner to a pedal for operating the braking system. The forward end of the boot is secured over the flange 25 by a spring clip 38 and the forward end of, the piston rod 31 is formed with a ball head 39 through which it is secured to a plunger or piston 40. i i

i The plunger 40 is formed with a head 4| which substantially fills the bore of the cylindrical portion I5 and as an aid in sealing the bore, carries The cup 42 may be made of rubber or other suitable material and serves to prevent the passage offluid rearward past the head 41. The cup 42' is secured in an annular groove 42 by means of a circular flat spring ring 44. The plunger 40 is provided with a rearwardly extending cylinder '45 which telescopes withina sleeve 46 formed witha rear ward flange 41 for limiting the rearwarcl movementof the piston 39 and with afixed head 48 substantially filling the bore of the portion I6 and serving as a support" for an annular sealing cup 49.

The sleeve, 46 and thehead 4B are prevented from being displaced rearwardly by means of a spring stop 5| seated in a groove 52 and are prevented from being displaced forwardly by means of a tubular member 63 which bears at its forward end against the shoulder formed by the junction between the portions I 5 and I6 and bears at its rearward end on the annular cup 66 thus serving not only to position the cylinder 66 but also serving to maintain the cup 66 in the desired position. The movable head 6I and the fixed head 66 are each formed with a plurality of small ports such as 56 and 55 respectively through which fluid may pass forwardly- The wheel cylinder I2 comprises a cylindrical casting 6| formed with an up-standing annular flange or boss 62 which forms a well within which there is positioned a ball 66 normally adapted to seat upon a cooperating valve seat 66 and to prevent the escape or ingress of fluid through the boss which thus forms a bleed opening. The projection 62 is formed with threads and a vented plug 66 having a wrench receiving head is screwed into said projection and normally maintains the ball 66 upon its seat. Positioned in the casting H are a pair of plungers or pistons 66 and 61. each formed with a pair of annular grooves such as 66 and 66, and 1| and 12 respectively. The grooves 66, 66, 1|; and 12 are provided with packing cups 16, 16, 16, and" respectively. said cups serving to prevent the exit or ingress of fluid from or into the wheel cylinder. It is to be noted that the cups 16 and 16 face outward while the cups 16 and 16 face inward. The plunger 66 is provided with a port 11 leading from the interior of the wheel cylinder to the groove 66' and with a port 16 leading to the atmosphere from the'groove 66. The plunger 61 is similarly providedwith ports 16 and 6|. The plungers are also provided with inwardly extending projections 66 and 66 which position the plungers to insure that the inlet opening 62 from the conduit I6 shall always remain open. a

In preparing the hydraulic brake system shown in Figure 1 for operation, the plug 26 and the valve 66 are removed and the reservoir 26 is filled with suitable liquid. 'The plug 66 is backed off from its seat so as to allow the check valve 66 to moveiat times oi! of its seat in the bleeding operation. Reciprocation of the rod 61 and the piston formed by. the movable head by means of the pedal. forces any air trapped in the system out past the check valve 66 on the forward stroke and at the same time draws liquid from the reservoir 26 through the port 26 and into the chamber formed between the fixed head 66 and the movable head 6|. 0n the rearward stroke liquid. from between two'heads is sucked past the movable head by reason of the vacuum created in the system ahead of said movable head. 0n the next forward stroke, this liquid together with the trapped air is'forced out past the check valve 66. Reciprocation is continued until the system is completely filled with liquid and until all air is driven out from thesystem.

Thereupon the plug 66 is screwed down to maintain the check valve 66 upon its seat and the valve 36 and the plug 26 are reinserted in the position shown in the drawings. Thereafter, reciprocation of the plunger 66 serves to apply the brakes through the wheel cylinder. When the reservoir'is first filled and bled and the as sembly including the plug 26 inserted, the pressure on the liquid in the reservoir is approximately atmospheric; The movement of the plunger cylinders 66 forward forces liquid to the .wheel and thus lowers the pressure in the Y for the same operation.

reservoir. On account of this lowering of pressure and because no air can enter through the valve 66, some air is drawn in through the vent 36 and the ports 55 and is subsequently compressed in the upper end of the reservoir 26 to maintain the liquid in the system under super- 6 charged pressure. the amount of such pressure being controlled by the weight of the spring 62.

The brake system shown in Figure 2 comprises a reservoir 66, a master cylinder 66, and wheel cylinder 6|. The reservoir 66 is provided with a partition 62, a cover 66, and a liquid level indicator 66.. It has outlet openings 66 and 66 which are connected to the master cylinder 62.

The master cylinder 66 has a plunger 61 provided with a plurality of annular sealing cups such as 66. 66. and IN the first named facing forward and the last two named being reversed relative to each other and positioned toward the rear. By reason of these cups, fluid is prevented from leaving or entering the cylinder except through openings I62 and I 66 which are connected with the openings 66 and 66 respectively of reservoir 66 or throughopenings I 66 and I 66 connected with the front and tively.

The plunger 61 slides through a head I66 which is secured within the cylinder 66 so as to be allowed a limited longitudinal movement therein. the head being provided with ports such as I61, I66, and I66 communicating with the opening of I62. Rearwardly of the head I 66, there is provided an annular packing cup II6 rearwardly and is held in position by a tubular member III which may be formed if desired by a short section of pipe. Forward of the head I66 there is provided a similar packing cup I I2 which faces forwardly and is held in position by a similar tubular member II6. It is to be noted that the length of members III and H3 as well as the rear brakes respecsroove in which the head I66 is seated allow a slightlongitudinal movement of the head I66 and with it. the-cups I66 and H2 so as to allow equalizing of pressure between the front and rear brakes. v v

The wheel cylinder 6|, is substantiallythe same as the cylinder I2 previously described and is provided with an annular boss or projection 6 corresponding to the projection 62. However, a tubular member I I6 is provided for holding the cups I I6 and H1 in position when the fluid in the cylinder is not under brake applying pressure. In? to be understood that when operating pressure is applied to the fluid, the fluid itself maintains the cups in their position. The plungers are also provided with additional packing cups 6a and I I1a smaller in area and facing outward. The projection H6 is internally threaded as at H6 and has screwed therein a plug II6 formed with a conical end adapted to seat in a conical shaped valve seat concentric with the projection H6. The plug H6 is itself formed with a tapped opening I26 and with intersecting bores I2! and I22. A-bleeding hose I26 provided with a check valve I26-is adapted to be threaded into the tapped opening I26 for the bleeding operation, the plug II6 being adapted to be loosened In the operation'of the braking system shown in Fig. 2, pressure applied by the pedal isiadapted to'move the plunger 61 forward, thus immediately closing the port leading to the opening I66 and forcing fluid through the outlet opening I66 to the front brakes and through the outlet opening I66 to the rear brakes. The displaced fluid creates which faces i g "In the bleeding opera. ion the plug] I8 is backed i ofiwslightlyi'rom its {seat and the bleeding hose I23 is attached. Then liquid is forced to the 15 wheel cylinders by: movement of the piston and is thence forced out past. the check valve I24 carrying :with it any airwhich maybe trapped in the system. -On the-retum stroke, the check valve I24 prevents airfrom returning. into the l 20 wheel cylinder and additional liquid is drawn into themaster cylinder through the opening I02 and then through? the bores I01, l00,-and I03 and past thecups I I0 and1| I2. Should an excess of pressurebewdeveloped in the system, the pressure 25 i may be relieved through i openings I03 and i I I4 -when-the parts are in the brake-oil. position It istobe understood thatduring the bleedingoperation, the plug H8 is backed of! slightly from its seat. 1 3o :1 In Figure 3; I have shown abmodifled form of cylinder somewhat similarto that shown in Fig- ;ure 2,,but differing in certain details therefrom.

The masterscylinder I3I- has. formed integrally Kyftherewith :a covered annular flange I32 which i 35' serves as. a combined reservoir andpressure chamher for 'supercharging the system. Positioned in thefiange I32 is an invertedncontainer I33 formed with a flange I34. The container is normally urged downward into contact with an annular packing plate I35 by means of a compression spring I36 which at its lower end bears upon the flange I34 and at its upper end bears against the cover I31.for the flange I32. The cylinder I3I is also provided with two other smaller anfnular flanges I30 and I38a, neither concentric with the flange I32. Inthe well formed by the ing cup I39 having an L-cross section. The cup I39 covers ports I40 and I4I which allows liquid to flow into the interior of the container I33 from the ports I40 and HI but-prevents liquid from passing out through the ports I40 and MI from the interiorof the container I33. The port I leads to a chamber I42 formed between a shoulder I43 provided in'the cylinder Ill and a head or piston I44 formed at the rear of the plunger I65, the port I40 normally leading forward of that chamber. 'Coacting with the head a m a CA I44 is an annularsealing cup I45 which prevents the passage of fluid rearward past the head; The plunger I45 is also formed with a forward head 141 provided with a sealing cup I40, the head and the cup forming a piston and being normally positioned just rearwardlyof the port I40 and .forwardlyof the point at which the port I connects with the chamber I42; I when the plunger is operated, however, the piston is moved forward past the port I40. The chamber I42 is also provided with an opening I43 connected through the I32. outside of a. container I33 the reservoir outside of the container being vented to theatinosflanges I38 there is positioned an annular sealwell formed bythe flange I381: with the reservoir valve allowing liquid to flow in from the reserf voir I32-to the chamber I42 but preventing liquld from passing, fromthe chamber to the reservoir. The cylinder I3I is provided with an equalisinghead I52 corresponding substantially with the head I06 and with cups I53I.1and I54,.corresponding substantiallyto. the cups H2 and IIII.

The cup I53 however, is normally maintained upon its seat by means of a spring I55which also position. Liquid is suppiedto the passageways formed in the head I52 through a diagonal port I56 which leads to the interior of the container m. H

Before operation of this form of master bylin der, liquid is poured. into the reservoir I32. Op-

eration of the plunger I45 forces air, trapped in the cylinders through the openings I51 and I53 to the forward and rear brakes respectively and out of the wheel cylinder past a check valve such as one of the check valves 53 or I24. On the rearward stroke, liquid isdrawn into the chamber! past the check valve, I 5I. Subsequent "forward strokes force the liquld drawn into chamber I42 through port I into the container I33 and thence through the port I56 past the cups I53 and I54 to theiorward brake system and. the rearbrake system. ifter the system has been filled with liquid; slight losses of liquid fromthe i forward brake. system may be, compensated for bypassage of liquid forward past the cup I48. as

normally urges the head I52 toward its rearward well a by passage of liquid rearward past the cup I54. sses of liquid in the rearbrake systemare compensated by passage of liquid past the cup I53. 1 Repeated operations of the plunger serve.

to supercharge the pressure by drawing in liquid past the valve I5I and forcing it throughthe port I4I into the container [Hand to the topof said containeruntil the pressure therein reaches the weightof thespring I36 whereupon the pressure In the container I33 may be relieved back to the main part of the reservoir I32 by lifting the container oil of the packing I35.

- The modified form of master cylindershown in Figure 4 is very similar to: that shown in Figure 3 but is, considerably simpler and cheaper to construct inasmuch as no arrangements are provided for separate systems for the front and rear; brakes. Therein the cylinderiil has a plunger I62 which corresponds substantially to the plunger I45, a reservoir I53 which corresponds substantially to the reservoir I32, and a. container I54. which corresponds substantially to the container I33. The check valve I65 corresponds substantially to the check valve I5I,,.and the cups I68, I01, I05 correspond substantially to .the cups I45, I43, and I54. A port I corresponding to the port I leads to an annular recess "I which corresponds substantially to the recess for the i equalizing head I52. However, an annular flanged packing I12 which has an L shape in cross section'fulfills the functions of the annular pack ing I34and alsofulfllls part of the functions of the cup I33 in serving as a one way check valve for the port I13. The port I14 is closed only when covered by the cup I01. An outlet port I15 at the forward end' of the cylinder is located in the center of the cup I58 and leads to all of the wheel cylinders'ofthe front and rear brakes.

The operation of this form of my device is substantially the same as that shown in Figure 3,

with the exception that no provision ismade for keeping the front brakesystem separate from the rear brake. system.

' "l'he inventions relating to wheel cylinders are also shown and are claimed in my copending application Serial No. 23,426, filed May 25, 1935.

The inventions relating to the master cylinder shown in Figure 2 is alsov shown and is claimed 5 in my copen'ding application Serial No. 23,425,

filed May25, 1935. I

It is to be understood that the above described embodiments of my invention are for the purpose of illustration only and various changes may be flmade therein without departing from the spirit 20 wardly extending portion; means for reciprocatring said plungerfor increasing the size of the compartment-formed between said head and said plunger; and a reservoir associated with said master cylinder; having a port connecting the reser- 25 voir with said compartment, and having a spring loaded valve opening to the atmosphere.

'2. In a master cylinder a rear head formed with a plurality of ports,v an annular cup packing associated with said head and positioned in advance I thereof for preventing the passage of fluid rear- "wardly through said ports but allowing the passage or fluid forwardly through said ports, and a rubber boot covering the rear end of said cylinder for preventing the'ingress ofdust and dirt but 35 formed with a vent opening for allowing air. to pass into said boot and through said'ports' into said cylinder.

3. In a hydraulic brake system a mastercylinder having a forwardly extending portion of rela- 40 tively small diameterand a rearwardly extending portion of relatively large diameter; a fixed head for said rearwardly extending portion formed with portsand provided with an inwardly opening cup valve; a movable plunger in said brakes; a master cylinder formed with a compensating port and a supply port and having a forwardly extending portion of relatively small diameter, a rearwardly extending portion of relatively large diameter, a fixed head provided with a packing and positioned in said rearwardly extending portion, and a rearwardly extending sleeve associated with said fixed head; a movable plunger including a movable head normally positioned between said ports, provided with a packing for developing brake applying pressure, and forming together with said fixed head a compartment therebetween, and a rearwardly extending cylindrical piston portion slidably mounted in said sleeve and extending through said fixed head into said forwardly extending portion; means for reciprocating said plunger so that the forward movement thereof increases the size of the compartment formed between said head and said plunger; a reservoir connected with the compensating port and connected with the supply port of;

the-master cylinderbetween said fixed head and said movable head so the forward movement of said plunger serves to draw liquid in from said reservoir; and a fluid connection between the forward end of said master cylinder and said brakes.

' EUGENE G. CARROLL. 

